Concrete is one of the primary building materials used worldwide. One common form of concrete used in construction is “ready-mix” concrete, which is produced in accordance with a given formula at a plant and then trucked to a jobsite. At the jobsite, the concrete is off-loaded from the truck, as required to form a desired structure. Any excess or residual concrete left in the truck is then typically washed-out at the jobsite.
One current wash-out practice is to dig a pit in the ground and line it with plastic film. Ready-mix trucks dump any excess concrete into the pit and use roughly 15-20 gallons of water to rinse the truck and chute. The typical concrete pump will dump approximately ¼ to ½ a cubic yard of concrete into the pit and then require 30-50 gallons of water for rinsing off the pump truck. The result is not only a significant amount of wasted water, but a significant amount of water contaminated with caustic concrete waste. Furthermore, washout pits normally remain uncovered and if it rains, the washout pit may overflow and cause further contamination of the soil around the pit. This overflow water can also run into storm drains and on into rivers and bays, and possibly even into the ground water.
Eventually, a small front-end loader or the like is used to break up the waste concrete in the washout pit and remove it to be crushed and recycled. During this process the plastic liner is ruined and any remaining concrete-contaminated wastewater leaks into the soil.
One known solution to the problem of waste concrete is to wash-out ready-mix trucks into roll-off trash dumpsters. However, these types of dumpsters are not watertight and much of the wastewater leaks out and soaks into the soil. Furthermore, concrete pump trucks cannot use these dumpsters and therefore must dump their extra concrete waste and the resulting wastewater onto the ground next to the dumpster. Moreover, dumpsters are also subject to rain contamination and overflow.
On some large road jobs, or at extra large commercial job sites, contractors will sometimes dig out a large washout pit (approximately ½ to 1 acre in size) and set up several large evaporation pits. This technique allows for the washout of trucks in one location followed by wastewater evaporation and periodic waste concrete removal from the evaporation pits. These washout pits are too large and too costly to build and maintain for use in the construction of new home communities or at small commercial job sites. Additionally, the problems of rain overflow and wasted water are not addressed by this technique.
Hence, new solutions are required for conserving water and minimizing environmental impact during the wash-out of concrete pouring equipment at jobsites.